1. Field of the Invention
This invention relates to a mold apparatus, an injection molding apparatus, and an injection molding method, which are used for the injection molding of a preform.
2. Description of the Related Art
So far, containers made of glass have preferably been used as containers for accommodating toilet lotions, milky lotions, etc. (will hereinafter be referred to as cosmetics containers). This is because the glass containers have an aesthetic appearance such as a profound feel or a quality appearance, and tend to stimulate consumers' appetite for buying them.
In recent years, the aesthetic appearance of containers formed from resin has been improved, and the resin containers have been put to use as cosmetics containers. However, the resin containers are still difficult to form with an aesthetic appearance comparable to that of the glass containers.
The cosmetics containers formed of glass are often formed in a large wall thickness, for example, for the emphasis of a quality appearance or a profound feel. Although the shape of the container is modified, as appropriate, in accordance with the contents, it is common practice to render the bottom considerably thick-walled, and the body uniformly thin-walled compared with the bottom. Like the shape of the cosmetics container formed from glass, the cosmetics container formed from resin is also provided with a thick-walled bottom and a uniformly thin-walled body. By so doing, an improvement in its aesthetic appearance may be achievable.
Such a cosmetics container is produced, for example, by injection-molding a bottomed tubular preform with the use of a resin material, such as polyethylene terephthalate (PET), as a raw material, and blow-molding this preform. When the bottom of the cosmetics container is to have a thick wall, it is necessary to impart a large wall thickness to the bottom of the preform.
The preform is generally formed by injecting and charging a molten resin into an injection space defined by a neck mold, an injection cavity mold, and an injection core mold (see, for example, Patent Document 1). In forming the preform by injection molding, the spacing between the injection cavity mold and the injection core mold is set to be wide. By this measure, the bottom of the preform can be formed with a large thickness.